The described invention relates to an apparatus and method for continuously producing constant weight portions of semi-solid matter, such as bread dough, from a large mass through a dividing mechanism at high production rates, and more particularly, to such apparatus and method whereby variations in the weight of each portion are minimized by automatically adjusting the rate at which the semi-solid matter is fed to the dividing mechanism.
Commercial dough production often involves production of large quantities of dough which are continuously divided into portions using various types of dividing mechanisms, such as a rotating knife or ram shear divider, into which dough is fed by motor driven dough feeding devices such as machine extruders, augers or pumps. In the case of dividing mechanisms which divide dough passing through the mechanism at a fixed interval, such as a rotating knife or ram shear divider, control of the portion size and therefore weight can be achieved by controlling the operating rate of the dividing mechanism by varying the frequency or speed of the motor driving the dough feeding device, such as an electrical motor powered auger or pump. Adjustments to the portion size can thus be made by varying the control voltage input to the variable frequency controller or variable speed controller for the feed motor.
A typical motor controller voltage input has a numerical voltage range from +5.0 to xe2x88x925.0 volts, thus allowing the complete range of available motor speeds or frequencies to be directed by varying the control input signal over a ten volt range. Weight control of divided dough portions has been carried out by varying control voltage inputs to feeding device motors according to the weights of dough portions obtained through the use of in-motion conveyor type checkweighing systems, such as weigh belts and weigh belt feeder systems. These apparatus, however are only capable of determining a projection of the actual static weight by collecting samples of output from a weight sensor as individual dough portions as well as the section of the conveyor belt supporting the portions pass over it. Also, as the weight samples are collected, the sensor accuracy can be affected by air currents, vibration from surrounding equipment, vibrations or harmonics generated by the dough portion""s movement on the conveyor and other physical effects.
Also, since it is necessary to use a weighing device with sufficient capacity to support the weight of the empty conveyor along with the weight of the dough portion to be weighed, larger capacity weight sensors must be used, which are much less sensitive than smaller weighing sensors of the same variety.
Additionally, due to the physical properties of extruded dough, it tends to adhere to any surface it contacts. To limit the amount of adhesion it is common for flour to be sifted onto the device transporting dough portions. In prolonged operation, flour may randomly accumulate in various locations along the transport mechanism, including in the area where weight measurements are taken, thus introducing errors in the weight indications.
Further, due to the semi-solid nature of raw dough, transporting dough portions by a belt conveyor requires that the plane of the initial conveyor belt be at a higher elevation than subsequent downstream conveyor belts to eliminate the possibility of the dough portion being forced downward through the transition between sets of conveyor rollers. Also, in a system employing an in-motion belt weighing mechanism, the abrupt transition of the dough portion from an upstream conveyor to the weighing conveyor can impart an impact or torsion force to the weight sensor, resulting in inaccuracies in the measured weight.
Additionally, there are physical constraints with in-motion weighing systems, including that the weighing conveyor must be of substantial length, generally at least thirty inches, which may create integration problems with existing equipment.
Another commonly used means of weighing divided dough portions involves the use of a static weigh scale, whereby an operator may randomly remove and weigh dough portions and perform a statistical calculation to determine what adjustment may be required. This method also has several disadvantages, including that substantial variations in any individual sample portions may unduly influence the adjustment and that removal of sample portions from the processing sequence may affect production efficiency.
Thus, a need remains for a system to continuously monitor and control the weight of divided dough portions at high production rates without human intervention. Preferably, such a system would minimize the variations in the weight of dough portions from a desired weight by automatically calculating and implementing precise adjustments to the controller of the dough feed mechanism that supplies the dough divider mechanism.
The present invention satisfies these needs and provides an apparatus and method for continuously monitoring the weight of divided dough portions at high production speeds, and is capable of providing correction signals proportional to the weight deviation of each dough portion or a predetermined number of portions in a sample group from the desired portion weight. The magnitude of the dough divider feed rate control adjustment signal is also configurable for the specific application requirements.
One embodiment of the present invention comprises a dough production mechanism, a dough feed mechanism, a dividing mechanism, a weighing mechanism, a weight signal processor to calculate and transmit appropriate control signals to the dough feed mechanism, a conveyor system configured to transport dough portions from the dividing mechanism to the weighing mechanism, a positioning mechanism to place dough portions on the weighing mechanism, and a propulsion mechanism which removes the portions from the weighing mechanism to a further conveyor or processing system.
The speed of the transport conveyor is variable to accommodate the range of production speeds. The conveyor bed preferably is formed in a trough shape so that as the dough portion exits from the divider mechanism, the forward motion of the conveyor forces the dough portion to the center of the conveyor belt. The conveyor preferably is equipped with flour sifters above the conveyor bed to flour the dough and prevent adhesion as it travels on the conveyor.
Each successive dough portion is placed on the weighing device by a positioning mechanism (means), which dampens the kinetic energy imparted to the dough portion by the conveyor system, thus allowing the dough portion to rest on the weighing device. The positioning means may comprise a deflector device located along the path of movement of the dough portion. When impacted by the moving dough portion, the deflector device dampens the motion of the portion by resisting displacement, such as counter forces with spring or elastomeric material resistance devices and/or the inertia or deflection of the device itself.
The weighing mechanism is preferably a freestanding device that can be positioned between the transport conveyor and a downstream processing or conveyor system. As the dough portion reaches the end of the conveyor, it impacts a suspended pivoting spring-loaded TEFLON(copyright) coated deflector plate located above the scale receptacle, thus causing the dough portion to rotate 180 degrees backwards as it falls from the end of the conveyor.
As the dough portion falls from the conveyor, the deflector plate directs the portion to the scale receptacle, which is coated with a non-stick material such as TEFLON(copyright) to prevent adhesion of the dough portion. The scale receptacle is supported by a load cell which provides an indication of the displacement of a resilient counter force due to the weight of the portion. Various types of counter forces, such as springs or elastomeric materials, can be used in the load cell. The displacement of the counter force can be measured most readily by devices which exhibit varying electrical properties under physical deformation or displacement, such as strain gages, transducers or forced motor. The analog electrical indications generated by the load cell can be converted by an analog to digital converter (xe2x80x9cA/Dxe2x80x9d) to a digital signal compatible for input to the weight signal processor. The load cell used in the weighing mechanism utilizes a load cell body or counter force that is submerged in an engineered high density fluid to provide impact cushioning and limit the post impact oscillation (xe2x80x9cringingxe2x80x9d) of the counter force due to the impact of the dough portion on the scale receptacle. Upon expiration of predetermined time delay interval to insure complete dampening of post-impact oscillation, a static weight of the portion is determined from the load cell indication by a weight signal processor.
After the weight signal processor converts the electrical indication generated by the load cell for the portion to a static weight datum and stores the datum, the dough portion is propelled from the scale receptacle to the downstream conveyor by a sweep paddle. The paddle is energized by a servo motor drive, solenoid or other motion control device. As the paddle begins its forward motion, air jets surrounding the scale receptacle discharge pressurized air to clear any loose flour from the scale receptacle. A vacuum collection port connected to a vacuum source collects and removes flour and other matter released from the receptacle.
Once the airborne dough portion is ejected from the scale receptacle, it impacts a second pivoting deflector plate, which forces the dough portion downward onto a downstream conveyor or other material handling device. This process is repeated for successive dough portions.
The weight signal processor compares the weight of each dough portion in each sample group to the desired dough portion weight and automatically calculates a signal which is sent to the controller of the dough pump supplying the dividing device to increase or decrease the amount of dough passing through the cutting mechanism during each cut cycle, thereby providing continuous divided dough weight monitoring and control.